Download Chapter 19: Human Genetics

Chapter 19: Human Genetics
1.
A)
B)
C)
D)
Ans:
Autosomes are
human chromosomes.
sex chromosomes.
nonsex chromosomes.
abnormal chromosomes.
C
2.
A)
B)
C)
D)
Ans:
A human female body cell contains
46 chromosomes.
44 autosomes.
2 X chromosomes.
all of these.
D
3.
A)
B)
C)
D)
Ans:
Down syndrome is due to an extra
X chromosome.
Y chromosome.
autosome.
X chromosome or an extra Y chromosome.
C
4.
A)
B)
C)
D)
Ans:
Which condition occurs as a result of nondisjunction?
Down syndrome
Turner syndrome
Poly-x syndrome
all of these
A
5.
A)
B)
C)
Ans:
The sex of a child is determined by the
sperm.
egg.
either sperm or egg.
A
6.
A)
B)
C)
D)
Ans:
Turner syndrome is due to a(an)
extra sex chromosome.
missing sex chromosome.
extra autosome.
missing autosome.
B
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7.
A)
B)
C)
D)
Ans:
Poly-x females are
never fertile.
hermaphrodites.
often fertile.
nonexistent.
C
8.
A)
B)
C)
D)
Ans:
YO individuals are
feminized males.
masculine females.
nonexistent.
normal males.
C
9.
A)
B)
C)
D)
Ans:
XYY are usually
super males.
sterile females.
males with speech and reading problems.
nonexistent.
C
10.
A)
B)
C)
Ans:
Which sex chromosome(s) is(are) needed for life?
X
Y
X and Y
A
11.
A)
B)
C)
D)
Ans:
In which situation can a child born with a genetic disease have two normal parents?
when the disease gene is dominant
when the disease gene is recessive
when the disease gene is either dominant or recessive
it is not possible
B
12.
A)
B)
C)
D)
Ans:
A sex-linked gene inherited by a male comes from the
father.
mother.
father or the mother.
father and the mother.
B
13. List four abnormal sex chromosome conditions, giving the characteristics of each.
Ans: See text.
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14. Give examples of dominant, recessive, and sex-linked genetic disorders.
Ans: See text.
15. Males are more likely to have a sex-linked disorder than females. Why does this
happen?
Ans: Males only have one X chromosome and therefore express (show the effects of) all Xlinked genes.
16. Persons with Down syndrome have an autosomal abnormality. Explain this.
Ans: Individuals with Down syndrome have inherited three copies of chromosome number
21.
17. Color blindness is considered a sex-linked recessive disorder. Explain what this means.
Ans: The gene that causes color blindness occurs on the X chromosome. Females require
two copies of this recessive gene in order to be affected. Males require only one copy of
the recessive gene.
18. Explain how Turner syndrome, Poly-x Syndrome, and Klinefelter syndrome may arise
as a result of nondisjunction during oogenesis.
Ans: Nondisjunction during oogenesis could produce an egg with two X chromosomes and an
egg with no X chromosome. If these eggs were fertilized with normal sperm (sperm
carrying either a single X chromosome or a single Y chromosome) these conditions
could result.
XX egg + X sperm = metafemale
XX egg + Y sperm = Klinefelter syndrome
no X egg + X sperm = Turner syndrome
19. If one parent has only dominant genes and the other has only recessive genes for a
particular recessive genetic disorder, how many of their children should be affected by
the disorder?
Ans: None, all of the children would have one dominant copy and one recessive copy.
20. If one parent has only dominant genes and the other has only recessive genes for a
particular dominant genetic disorder, how many of their children should be affected by
the disorder?
Ans: All of the children, as each would have one dominant gene and one recessive gene for
the disorder.
21. List the steps involved in the construction of a karyotype.
Ans: 1. Chemical is added to stop division of cells.
2. Slide is prepared by spreading cells on a slide, drying, and staining.
3. Slide is examined for cells with chromosomes.
4. Chromosomes are photographed, and then arranged by size and shape.
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22. Give a specific example of how gene therapy can be used to treat a genetic disorder.
Ans: The text describes ex vivo gene therapy for two genetic disorders, severe combined
immunodeficiency syndrome and familial hypercholesterolemia. In each case, tissue is
removed from the patient and infected with a retrovirus that carries the normal form of
the gene that causes the genetic disorder. The tissue is then replaced in the patient.
23. Is it possible for a dominant genetic disorder to skip a generation in a family line?
Explain your answer.
Ans: Yes, a dominant genetic disorder can skip a generation. This can happen when two
parents in a generation both have one dominant and one recessive copy of the gene in
question. Each child that they produce has a 25% chance of being born with two copies
of the recessive gene and therefore without the dominant disorder.
24.
A)
B)
C)
D)
Ans:
Which genotype is homozygous?
EE
ee
Ee
Both EE and ee are correct.
D
25.
A)
B)
C)
D)
Ans:
Carriers for recessive disorders are
homozygous dominant.
heterozygous.
homozygous recessive.
either heterozygous or homozygous recessive.
B
26.
A)
B)
C)
D)
Ans:
The study of genomics should lead to
new medicines.
safer medicines.
longer life.
All of these choices are correct.
D
27. Jan had an amniocentesis, which found her child appeared to be normal. What week of
her pregnancy was she in?
Ans: 14th-17th week.
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